Apparatus and Method for Sculpting the Surface of a Joint

ABSTRACT

Methods and devices for sculpting bones, particularly in preparation for implanting prosthetic devices to replace articulating bone joint surfaces. Improved bone removal devices including burr mills driven by gears and loop drives are provided. Reciprocating cutters and belt cutters are also provided. Some devices have either integral or removable expandable portions to vary the force and bone resection depth. Devices can have irrigation ports and plenums to remove bone fragments. Some cutters are dual cutters, adapted to remove bone in two or more regions, such as the knee joint, simultaneously.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 60/746,228, filed May 2, 2006, and is acontinuation-in-part of U.S. patent application Ser. No. 11/535,916,filed Sep. 27, 2006, which claims the benefit of U.S. Provisional PatentApplication No. 60/721,450, filed Sep. 28, 2005, and is acontinuation-in-part of U.S. patent application Ser. No. 10/429,435,filed May 5, 2003, the entireties of which are hereby incorporated byreference.

TECHNICAL FIELD

This invention relates to implants and instruments for use in cuttingand preparing bone, for example, in total and partial knee arthroplasty.Such instruments are applicable in other total and partial jointreplacement surgeries which include, but are not limited to the hip, theshoulder, the ankle, the elbow, the joints of the hand, the joints ofthe wrist, the joints of the foot and the temporal mandibular joint,articulating joints such as the knee and hip, and also motion segmentsof the spine.

BACKGROUND OF THE INVENTION

A joint, such as the ankle, knee, hip or shoulder, generally consists oftwo or more relatively rigid bony structures that maintain arelationship with each other. In the case of the spine, a motion segmentgenerally consists of two vertebral bodies, a disc and two facet joints.Soft tissue structures spanning the bony structures hold the bonystructures together and aid in defining the motion of one bony structurerelative to the other. In the knee, for example, the bony structures arethe femur, tibia and patella. Soft tissue structures spanning the kneejoint, such as muscles, ligaments, tendons, menisci, and capsule,provide force, support and stability to facilitate motion of the knee.Muscle and tendon structures spanning the knee joint, as in other jointsof the body and in the spine provide dynamics to move the joint in acontrolled manner while stabilizing the joint to function in an orderlyfashion. The joint is dynamically stabilized by contraction of primarymuscles to move the joint in a desired direction combined withantagonistic muscle contraction to direct resultant joint loads withinfavorable orientation limits relative to the bony structures of thejoint. It is believed that proprioceptive feedback provides some of thecontrol or balance between primary and antagonistic muscle contraction.

In an articulating joint, a smooth and resilient surface consisting ofarticular cartilage covers the bony structures. In the spine, the disc,consisting of an annulus and a nucleus, spans the space between adjacentvertebral bodies and two facet joints provide articulation posteriorly.The articular surfaces of the bony structures work in concert with thesoft tissue structures spanning the joint to form a mechanism thatdefines the envelop of motion between the structures. Within a typicalenvelop of motion, the bony structures move in a predetermined patternwith respect to one another. When articulated to the limits of softtissue constraint, the motion defines a total envelop of motion betweenthe bony structures. In the knee, the soft tissue structures spanningthe joint tend to stabilize the knee from excessive translation in thejoint plane of the tibiofemoral compartments. Such tibiofemoralstability enables the femur and tibia to slide and rotate on one anotherin an orderly fashion. The motion of the patella relative to the femurin the patellofemoral compartment is related to tibiofemoral motionbecause the patella is linked at a fixed distance from the tibia by thepatellar ligament.

Current methods of preparing a joint to receive implants that replacethe articular surfaces or motion segments involve an extensive surgicalexposure. In traditional total knee arthroplasty, the surgical exposure,ligament release and sacrifice of the anterior cruciate ligament must besufficient to permit the introduction of guides that are placed on, in,or attach to the femur, tibia or patella, along with cutting blocks toguide the use of saws, burrs and other milling devices, and otherinstruments for cutting or removing cartilage and bone to provide asupport surface for implants that replace the artificial surfaces ormotion segment. For traditional knee joint replacement, the distal endof the femur may be sculpted to have flat anterior and posteriorsurfaces generally parallel to the length of the femur, a flat endsurface normal to the anterior and posterior surfaces, and angled flatsurfaces joining the above mentioned surfaces, all for the purpose ofreceiving a prosthetic device. In general these are referred to as theanterior, posterior, distal and chamfer cuts, respectively. In currenttotal knee arthroplasty proper knee alignment is attained bypreoperative planning and x-ray templating. Anterior-posterior (A/P) andlateral x-ray views are taken of the knee in full extension. Themechanical axis of the tibia and of the femur is marked on the A/Px-ray. The angle between these lines is the angle of varus/valgusdeformity to be corrected. In the A/P view, the angle of the distalfemoral resection relative to the femoral mechanical axis, hence theangle of the femoral implant, is predetermined per the surgicaltechnique for a given implant system. Similarly, the angle of the tibialresection relative to the tibial mechanical axis, hence the angle of thetibial implant, is predetermined per the surgical technique for a givenimplant system. The femoral resection guides are aligned on the femur toposition the distal femoral resection relative to the femoral mechanicalaxis and the tibial resection guides are aligned on the tibia toposition the proximal tibial resection relative to the tibial mechanicalaxis. If the cuts are made accurately, the femoral mechanical axis andthe tibial mechanical axis will align in the A/P view. Once the femurand tibia have been resected, the medial and lateral collateralligaments may be released to balance the knee. Soft tissue balancing isgenerally done with the knee in full extension. The spacing between thefemur and tibia at full extension is used to guide ligament release toattain an appropriate extension gap.

Typically, an appropriate extension gap is evidenced by parallelorientation of the distal femoral resection to the tibial plateauresection and with a gap sufficient to accommodate the femoral andtibial implants. This approach addresses knee alignment and balancing atfull extension. Knee alignment and tissue balance at 90° of flexion isgenerally left to surgeon judgment and knee alignment and tissue balancethroughout the range of motion has not been addressed in the past. Inaligning the knee at 90° the surgeon rotates the femoral component aboutthe femoral mechanical axis to a position believed to provide propertensioning of the ligaments spanning the knee.

Current implants and instruments for joint replacement surgery havenumerous limitations. These relate to the invasiveness of the procedureand achieving proper alignment, soft tissue balance and kinematics ofthe joint with the surgical procedure. Such difficulties are present inall joint replacement surgery. Although the spinal disc is not anarticular joint, interest in restoring the kinematic function of adegenerated disc has lead to spinal arthroplasty incorporating metaland/or plastic articulating surfaces. Polymers, including hydrogels andurethanes, have also been used to restore spinal disc function. Suchspinal implants are preferably placed via minimally invasive surgicalapproaches and restore motion and kinematics, hence require accuratealignment and orientation of the implant components one to another. Inaddition, the kinematics of a spinal motion segment are defined by thecombined motion across the disc which is a function of the annulus,nucleus, anterior ligament, posterior ligament, facet joint articulationand muscles spanning the motion segment. A spinal motion segment is themotion between adjacent vertebral bodies.

A difficulty with implanting modular knee implants in which the femur ortibia is resurfaced with multiple components has been achieving acorrect relationship between the components. For ease of description,multiple components comprising a component such as a femoral componentwill be referred to as subcomponents. For example, a modular femoralcomponent may include subcomponents for the trochlea, the lateralfemoral condyle and the medial condyle, and reference to a “femoralcomponent” includes subcomponents in the case of a multi-piece femoralcomponent.

In the case of a plurality of subcomponents resurfacing the distal femuror proximal tibia, the orientation and alignment of the subcomponents toeach other has largely not been addressed. This may account for the highfailure rates in the surgical application of free standing compartmentalreplacements used individually or in combination. Such compartmentalreplacements include medial tibiofemoral compartment, lateraltibiofemoral compartment, patellofemoral compartment and combinationsthereof. Component malalignment may account for the higher failure rateof uni-compartmental implants relative to total knee implants asdemonstrated in some clinical studies. When considering bi-compartmentaland tri-compartmental designs, orientation and alignment ofsubcomponents, as well as components, is critical to avoid acceleratedwear with a mal-articulation of the implant.

Surgical instruments available to date have not provided trouble freeuse in implanting multi-part implants wherein the distal femur, proximaltibia and posterior patella are prepared for precisesubcomponent-to-subcomponent and component-to-component orientation andalignment. While current femoral alignment guides aid in orientingfemoral resections relative to the femur and current tibial alignmentguides aid in orienting tibial resections relative to the tibia, theyprovide limited positioning or guidance relevant to correctsubcomponent-to-subcomponent alignment or orientation. Nor do suchalignment guides provide guidance relevant to soft tissue balance (i.e.ligament tension to restore soft tissue balance). Moreover, they providelimited positioning or guidance relevant to correct flexion/extensionorientation of the femoral component, to correct axial rotation of thefemoral component, nor to correct posterior slope of the tibialcomponent. For the patellofemoral joint, proper tibiofemoral alignmentis required to re-establish proper tracking of the patella as defined bythe lateral pull of the quadriceps mechanism, the articular surface ofthe femoral patellar groove and maintaining the tibiofemoral joint line.For optimum knee kinematics, femoral component flexion/extension andexternal rotation orientation, tibial component posterior slope andligaments spanning the joint work in concert maintaining soft tissuebalance throughout the knee's range of motion.

For patients who require articular surface replacement, includingpatients whose joints are not so damaged or diseased as to require wholejoint replacement, the implant systems available for the knee haveunitary tri-compartmental femoral components, unitary tibial components,unitary patellar components and instrumentation that require extensivesurgical exposure to perform the procedure.

It would be desirable to provide surgical methods and apparatuses thatmay be employed to gain surgical access to articulating joint surfaces,to appropriately prepare the bony structures, to provide artificial,e.g., metal, plastic, ceramic, or other suitable material for anarticular bearing surface, and to close the surgical site, all withoutsubstantial damage or trauma to associated muscles, ligaments ortendons, and without extensive distraction of the joint. To attain thisgoal, implants and instruments are required to provide a system andmethod to enable articulating surfaces of the joints to be appropriatelysculpted using less or minimally invasive apparatuses and procedures,and to replace the articular surfaces with implants suitable forinsertion through small incisions, assembly within the confines of thejoint cavity and conforming to prepared bone support surfaces.

BRIEF SUMMARY OF THE INVENTION

The present invention is related to implants and instruments for use inless and minimally invasive total knee replacement surgery. Moreparticularly, this invention relates to instruments for cutting andpreparing bone. Such bone cutting instruments are applicable in totaland partial knee arthroplasty. In addition, such instruments areapplicable in other total and partial joint replacement surgery toinclude, but not limited to the hip, the shoulder, the ankle, the elbow,the joints of the hand, the joints of the wrist, the joints of the footand the temporal mandibular joint. Such instruments are also applicableto motion segments of the spine to include, but not limited to thespinal disc and the facet joints. For the purposes of this document, theterm joint will be used to refer to articulating joints such as the kneeand hip, and also motion segments of the spine.

The present invention provides a system and method for partial or totaljoint replacement, that is to resurface one or more of the bony surfacesof the joint or motion segment, which involves less or minimallyinvasive surgical procedures which can be used to place implants thatrestore joint kinematics. The instruments and implants disclosedaccomplish accurate bone and soft tissue preparation, restoration ofanatomical alignment, soft tissue balance, kinematics, component tocomponent orientation and alignment, subcomponent to subcomponentorientation and alignment, and implant fixation through limited surgicalexposure.

Proper alignment and positioning of the implant components andsubcomponents are enabled by instruments guided by the soft tissuestructures of the knee to guide bone resections for patient-specificanatomical alignment and component orientation. The medial and lateraltibial articular surfaces and the patellar articular surface aregenerally prepared with planar resections. The medial and lateralfemoral condyles and trochlea are kinematically prepared. Suchinstrumentation is referred to as Tissue Guided Surgery (TGS) and isdescribed in U.S. Pat. No. 6,723,102 and is incorporated by reference inits entirety.

Proper alignment of the femoral, tibial and patellar implants requiresproper anatomical alignment of the knee joint throughout the range ofmotion. By using the soft tissue structures spanning the knee to guidebone resection, TGS instrumentation established proper soft tissuebalancing throughout the range of motion. Current knee implant systemsgenerally balance soft tissue structures in full extension only. In atypical TGS knee procedure the knee joint is exposed through a smallmedial patellar incision. The anterior and posterior cruciate ligamentsare left intact. Applicants believe that the instrument system willfunction in cases where the anterior cruciate ligament is partially orcompletely compromised. In one embodiment of the invention describedherein, the medial and lateral tibial articular surfaces are removedwith planar resections and bone sculpting instruments are placed on theresected surfaces in the medial and lateral tibiofemoral compartments.Each sculpting instrument is extended to load against its respectivefemoral condyle and the knee is flexed and extended to kinematicallyprepare the femoral condyles. Alternatively, the knee can be positionedat specific flexion angles. At each knee flexion angle each sculptinginstrument is extended to load against its respective femoral condyle toprepare a planar surface on respective femoral condyle. Sculptinginstruments are retracted and the knee is flexed to the next specificangle and each sculpting instrument is extended to load against itsrespective femoral condyle to prepare multiple planar surfaces.Optionally, the sculpting instruments can be structured to prepare acurved, hemi-spherical or contoured surface as may be required to matchvarious support surfaces on a mating unitary femoral implant or afemoral implant structured with a plurality of sub-components.

As the femoral condyles are sculpted by TGS instruments, varus/valgusalignment at full extension is periodically checked. Intracompartmentaldistraction of the sculpting instrument is biased to the medial orlateral tibiofemoral compartment for valgus or varus correction,respectively. Alternatively, medial and lateral femoral condyles areprepared simultaneously until appropriate resection depth is reached onone condyle. The sculpting instrument in this compartment is replacedwith a spacer and preparation of the other femoral condyle is continueduntil anatomical align of the knee is attained. When the femoralmechanical axis and tibial mechanical axis align, the knee is properlyaligned. The surfaces of the femoral condyles have been progressivelyprepared by the TGS instruments guided by knee kinematics established bysoft tissue structures spanning the knee. Therefore, proper kneealignment and soft tissue balance is attained throughout the range ofmotion.

In an alternative technique, each tibiofemoral compartment is preparedindependently. The knee joint is exposed as described above. One of thetibiofemoral compartments is prepared first, typically the one with moresevere pathology. The respective tibial articular surface is resected asdescribed above and a sculpting instrument placed on the resection. Thesculpting instrument is extended to load against the femoral condyle.The knee is flexed and extended until the appropriate resection depth isreached. The sculpting instrument is replaced with a spacer. Theremaining tibiofemoral compartment is prepared next by resecting thetibial articular surface as described above. Placing a sculptinginstrument onto the resected surface and extending the sculptinginstrument to load against the femoral condyle. The knee is flexed andextended while monitoring varus/valgus alignment. Femoral condyleresection is continued until the desired anatomical alignment of theknee is attained.

The patellofemoral compartment is prepared in a manner similar to thetibiofemoral compartments. The patellar articular surface is removedwith a planar resection. Spacers are placed in the medial and lateraltibiofemoral compartments to maintain knee kinematics. A bone sculptinginstrument is placed on the resected patella and extended to loadagainst the femoral trochlea. The knee is flexed and extended tokinematically prepare the femoral trochlea. Trochlear resection iscomplete when the desired resection depth is attained. The surgicaltechnique described above has preparation of the patellofemoralcompartment following preparation of the femoral condyles. The sequencecan be reversed with the patellofemoral compartment being preparedfirst, a spacer placed in the patellofemoral compartment to maintainknee kinematics followed by preparation of the tibiofemoralcompartments. In this case the tibiofemoral compartments can be preparedsimultaneously or independently. Alternatively, the femoral trochlea canbe resected with a cutting guide placed on the distal femur or medial tothe trochlea. A surgical saw, either oscillating or reciprocating, isplaced on or through the cutting guide to resect the femoral trochlea.

Alternatively, the femoral condyles and trochlea are preparedsimultaneously. The articular surfaces of the tibia and patella areremoved with planar resections. Bone sculpting instruments are placed onthe medial and lateral tibial resections and the patellar resection.Bone is resected from the femoral condyles and trochlea as describedabove. Resection depth is monitored on each condyle and the trochlea.When appropriate depth is reached in one compartment that sculptinginstrument is replaced with a spacer and sculpting of remaining surfacesis continued. Once a spacer has been placed into one of the tibiofemoralcompartments, resection of the other femoral condyle is continued untildesired knee alignment is attained. If resection of both femoralcondyles is completed before completion of the trochlear resection, thesculpting instrument in the remaining tibiofemoral compartment isreplaced with a spacer and sculpting of the trochlea is continued to theappropriate depth.

Femoral, tibial and patellar bone resections attained with TGSinstrumentation are properly positioned and orientated for anatomic kneealignment, soft tissue balance and kinematic function throughout kneerange of motion. Using these bone support surfaces to position andorientate the femoral, tibial and patellar components, respectively,will maintain anatomic knee alignment, soft tissue balance and kinematicfunction. In general, the tibial and patellar resections are planar,making placement of the corresponding implant components, which haveplanar support surfaces, straight forward. The femoral resection is notplanar, and the relative position of the lateral condyle, the medialcondyle, and the trochlear resections to one another is a function thekinematics of a given patient. Therefore, the femoral implant shouldaccommodate this variability.

In an alternative embodiment surgical navigation is used in conjunctionwith TGS instrumentation to kinematically prepare the femur, tibia andpatella to support knee implant components. Surgical navigationtechnologies applicable to this approach include, but are not limitedto, image and image free navigation systems and Hall Effect basednavigation systems. The knee joint is exposed as described above.Navigational trackers are attached to the femur, tibia and patella. If atracker can not be attached to the patella, then tracking of the patellais done periodically or at discrete points during the procedure with atracking stylus. Pre-operative alignment and kinematics of the knee aremeasured per the protocol for the navigation system being used. Thetibial plateau and patella are prepared as described above.Alternatively, the navigation system is used to position tibialresection guides for resection of the medial and lateral tibialarticular surfaces. The navigation system may be used to align apatellar resection guide for resection of the patella. The anterior andposterior cruciate ligaments are left intact. Bone sculpting instrumentsare placed in the medial and lateral tibiofemoral compartments and thepatellofemoral compartments. The sculpting instruments are extended toload against the respective condyle or trochlea. The knee is repeatedlyflexed and extended to initiate bone resection in all threecompartments. The navigation system monitors and displays femoralresection depths for each compartment throughout the range of motionwhile monitoring knee alignment and kinematics. The navigation systemindicates when appropriate resection depth is attained on one of thefemoral condyles and signals the surgeon to replace that sculptinginstrument with a spacer. Femoral resection is continued until thenavigation system indicates that desired knee alignment is attained. Thesurgical navigation system monitors trochlear resection depth andnotifies the surgeon when the desired depth is attained. If appropriatetrochlear resection depth is attained before completing femoral condylarresection, then a spacer can be placed in the patellofemoral compartmentand femoral condylar resection continued. This technique describes usingsurgical navigation in conjunction with TGS instrumentation to preparethe three compartments of the knee simultaneously. In addition, surgicalnavigation can be used in conjunction with TGS instrumentation toprepare the knee compartments in the sequences and combinationspreviously described.

The sculpting instruments in the TGS instrumentation can be instrumentedwith sensors to measure intracompartmental distraction force anddistraction distance. Such instrumentation enables monitoring of softtissue balance during sculpting throughout the full range of motion.Force and displacement sensors can be attached to the ligaments spanningthe knee as complementary measurements of soft tissue balance,distraction force and distraction displacement. Instrumented sculptinginstruments also enable monitoring resection depth during sculptingthroughout the full range of motion. Load cells are placed in asculpting instrument to measure distraction force. Alternatively, ifhydraulic pressure is used to extend the sculpting instrument, thenpressure sensors are used to measure distraction force by multiplyingpressure applied by the cross sectional area of the hydraulic actuatoror bladder or balloon. Displacement sensors are placed in a sculptinginstrument to measure distraction distance. Alternatively, if hydraulicspressure is used to extend the sculpting instrument, then change involume of fluid delivered to the hydraulic actuator or bladder orballoon by calibrating the distraction device for displacement vs.volume change. Distraction load and distraction displacement readout canbe with a digital readouts, bar graph or other graphical display. Thereadout can also be displayed in a surgical navigation system display.Such instrumented sculpting instruments can be used with each of theprocedures and embodiments described above. Pressure to the hydraulicactuator or bladder may be provided by a syringe pump, or by apre-charged compliant bladder designed to maintain a relatively constantpressure in the fluid over a workable change in volume required toactivate the actuators or bladders used to distract the joint.Alternately, the distraction force can be applied by threadedmechanisms, inclined ramps or other mechanical means.

In a more sophisticated embodiment TGS instrumentation is integratedwith surgical navigation, intracompartmental distraction anddisplacement sensors, and programmable controllers to providesimultaneous closed loop control of the femoral resections. Thisapplication specific robotic system sculpts the femoral condyles andtrochlea while the surgeon repeatedly flexes and extends the knee. Theknee joint is access as previously described. A surgical navigationsystem and navigation trackers are applied as previously described andpre-operative alignment and knee kinematics are measured and archived.The tibia and patella are resected as previously described.Hydraulically extended sculpting instruments with integral distractionforce and distraction displacement sensors are placed into the threecompartments of the knee. The sculpting instruments are extended to loadagainst the respective femoral surface. lntracompartmental distractionforce in each compartment can be controlled by independent closed loopcontrollers with distraction force as the feedback. Alternatively,distraction displacement is used for the closed loop feedback for one ormore of the sculpting instruments. The robotic TGS instrument systemapplies a preliminary intracompartmental distraction force to the medialand lateral tibiofemoral compartments and to the patellofemoralcompartment, and indicates to the surgeon that the system is ready tostart femoral resection. The surgeon repeatedly flexes and extends theknee while the robotic TGS instrument system monitors resection depth,knee alignment and knee kinematics throughout the full range of motion.The robotic TGS instrument system is programmed to controlintracompartmental distraction force to advance resection depth in eachcompartment at generally the same rate until a preset condyle resectiondepth is attained, at which point the system prompts the surgeon toreplace that sculpting instrument with a spacer. The system thenmonitors knee alignment while the surgeon continues to flex and extendthe knee until the navigation system indicates desired knee alignment isattained. Replacement of the patellofemoral sculpting instrument with aspacer is prompted by the system when a preset trochlear resection depthis attained which may occur before or after completion of condyleresections. Alternatively, the robotic TGS instrument system isprogrammed to vary intracapsular distraction force between medial andlateral compartments with higher distraction force on the side requiringmore bone removal and reduced distraction force in the othertibiofemoral compartment. Tibiofemoral intracompartmental distractionforce is controlled in this manner until desired knee alignment isattained.

In another embodiment of the sculpting instrument the cutting elementsare designed for two modes of operation; on for cutting and off for nocutting. In the case of a sculpting instrument that uses shavingelements for bone cutting the blades are deployed for cutting andretracted for no cutting. Blade deployment and retraction is manual.Alternatively, blade deployment and retraction is actuated mechanicallyor hydraulically. For the procedures and embodiments described above,this on/off sculpting instrument eliminates the need for spacers. Whenthe desired resection depth or knee alignment is attained the respectivesculpting instrument is turned off. In the case of the robotic TGSinstrument system, the system controller is programmed to turnrespective sculpting instruments on and off to control resection depthin each compartment to attain a preset knee alignment while the surgeonis flexing and extending the knee. The system displays independentintracompartmental resection depths, knee alignment, soft tissue balanceand other variables of interest and prompts the surgeon when desiredknee alignment is attained. In another control mode, the robotic TGSinstrument system is programmed to monitor resection depth,intracompartmental distraction force and distraction displacement, andknee kinematics continuously throughout the knee's full range of motionand actively control bone resection in each compartment to varyresection throughout the range of motion to provide uniform soft tissuebalance, alignment and kinematics throughout the range of motion.

Although the application of the TGS instrumentation system to the kneeis described in detail herein, it is clear that the TGS instrumentationsystem is applicable to other total joint arthroplasty and to spinalarthroplasty is a similar manner. The combination of TGSinstrumentations with navigation and with closed loop control androbotics can have application in other joint and spinal arthroplastyapplications.

The present invention includes methods for sculpting the articularsurface of a first bone that normally articulates in a predeterminedmanner with a second bone. One method includes fixing one or morebone-sculpting tools to the second bone, sculpting the articular surfaceof the first bone by articulating the bones with respect to each other,and applying a distracting force between the bone-sculpting tool and thesecond bone. Optionally, sculpting the articular surface of the firstbone by positioning one of the bones with respect to the other, andapplying a distracting force between the bone-sculpting tool and thesecond bone. The distracting force is applied so as to tension the softtissue structures spanning the knee and force the bone-sculpting toolinto the first bone, in which the force applying is operated at least inpart under load control. An alternative method includes fixing one ormore bone-sculpting tools to the second bone, sculpting the articularsurface of the first bone by articulating or positioning one of thebones with respect of the other, and applying a first distraction forcebetween the tibia and femur so as to tension the soft tissue structuresspanning the knee. With the first distraction force applied, a seconddistraction force, independent of the first distraction force, isapplied between the bone-sculpting tool and the second bone so as toforce the bone-sculpting tool into the first bone. The first distractionforce is operated at least in part under load control. The seconddistraction force is operated at least in part under load control asmaterial is removed from the femur, said material removal continuinguntil bone-sculpting tool advances to a desired orientation and positionrelative to the second bone.

In some methods, applying the distracting force includes applying afluid under pressure, in which the load control includes controlling thefluid pressure. Controlling the fluid pressure can include controlling agaseous fluid pressure or a liquid fluid pressure, in variousembodiments. The method may include measuring the load between the twobones and controlling the distracting force at least in part as afunction of the measured load. In some methods, the force applying iscontrolled under load control, followed by displacement control after adisplacement limit is reached. The displacement control can includemechanically limiting the range of displacement.

In some such methods, the load control is at least in part performed byan automatic controller which automatically controls the distractionforce at least in part as a function of the load. The load control maybe at least in part performed under manual control, in which a humancontrols the distraction force at least in part in response to a loadread-out value.

Some embodiments utilize barrel cutters. One apparatus includes a framehaving a space within, an outside region without, and a plurality ofcutting cylinders rotatably disposed within the frame. A drive membercan be externally accessible from outside of the frame, and the drivemember operably coupled to rotate the cutting cylinders. In someembodiments, the housing has a posterior region for inserting into amammalian body, an anterior region opposite the posterior region, aright side and a left side both extending between the posterior andanterior regions, in which the drive member is a shaft which protrudesoutside of the housing through the right and/or left sides.

In some barrel cutter embodiments, the drive member is operably coupledto the cutting cylinders through gears. In others, the drive member isoperably coupled to the cutting cylinders through a flexible drive loop.Some embodiments also include a fluid inlet port and outlet port influid communication with the housing interior for providing irrigationand tissue debris removal. Embodiments may also include a plurality ofnested telescoping platforms, the platforms having an interior, anextended configuration and a collapsed configuration, in which theplatforms can be urged from the collapsed configuration to the extendedconfiguration through direct or indirect application of fluid pressureto the platforms interior. Some embodiments include two barrel cutterdevice coupled side by side in substantially the same plane, and whichmay be coupled to transfer applied torque between the first and seconddevices. In some embodiments two barrel cutters may be poweredindependently.

The present invention also provides belt cutter embodiments. Oneapparatus includes a frame having a posterior region for inserting intoa mammalian body, an anterior region opposite the posterior region, aposterior roller rotatably coupled to the frame posterior region, ananterior roller rotatably coupled to the frame anterior region, and acutting belt looped around both the posterior and anterior rollers. Theapparatus can further include a drive member operably coupled to theanterior roller to rotatably drive the anterior roller and cutting belt.

In some belt cutters, the cutting belt includes a plurality of aperturestherethrough, where which the apertures may optionally have a raisedtrailing edge. Some embodiments also include a posterior tissueprotector coupled to the frame to protect tissue from the cutting beltposterior region. The belt cutter may have an anterior frame membercoupled to the frame anterior portion. The drive member may beexternally accessible from outside the frame, with the drive memberdisposed along an anterior-posterior axis, or disposed perpendicular toan anterior-posterior axis, in various embodiments.

Some belt cutter apparatus further include a housing base operablycoupled to the frame for protecting tissue from a bottom portion of thecutting belt. A tensioning arm can be operably coupled to the anteriorand posterior roller for adjusting belt tension in some embodiments.

Some embodiment cutting belts have a longitudinal axis, a substantiallyplanar surface, and a plurality of outer cutting ridges disposed on thebelt outer surface. The belt may have a plurality of inner ridgesdisposed on the belt inner surface. The ridges are orientedsubstantially perpendicular to the belt longitudinal axis in someembodiments, and are oriented at between about a 20 and a 70 degreeangle with respect to the longitudinal axis in other embodiments. Thebelt may have a first set of substantially parallel cutting ridges onthe belt outer surface, and a second set of substantially parallelcutting ridges on the belt outer surface, in which the first and secondset of ridges cross each other to form a diamond shape pattern. In somebelts, a first set of substantially parallel ridges are disposed on thebelt outer surface, a second set of substantially parallel ridges aredisposed on the belt outer surface, where the first and second set ofridges are disposed at least a 20 degree angle with respect to eachother. Cutting belts can be tensioned and supported on rollers. Aposterior tissue protector is present in some embodiment devices. Somecutting belts have a hole trailing edge that forms a grater. One cuttingbelt has a cutting pattern with alternating, opposing, inclined ridgespartially spanning the belt. Cutting teeth can be directed anteriorly indirection of belt movement (i.e. the belt is rotating so as the superiorsurface is moving generally in an anterior direction) to urge the femurin an anterior direction while cutting.

The present invention also provides various reciprocating cutterembodiments. One such embodiment includes a frame having a posteriorregion for inserting into a mammalian body, an anterior region oppositethe posterior region, and a substantially planar upper cutting elementhaving a cutting surface. The apparatus also includes a drive memberoperably coupled to the cutter element so as to drive the cuttingelement to move substantially within a plane, in which the drive memberis accessible from outside of the frame. In some embodiments, the drivemember operable coupling is through an offset or eccentric cam. Somedrive members are disposed along an anterior-posterior axis, whileothers are disposed orthogonal to an anterior-posterior axis, in variousembodiments. Some embodiments include at least 2 upper cutting elements,each configured to operate in substantially the same plane.

In some reciprocating cutters, the upper cutting element cuts primarilyonly when moved in one direction, but not the opposite direction. Inothers, the upper cutting element cuts when moved in one direction andalso in the opposite direction. Some embodiments have adjacentsub-components or sub-cutting elements 180° out of phase to each other.Some embodiments have two or more sub-cutting elements; some have fourto six.

The present invention also provides an expandable apparatus for cuttinginto mammalian bone, where the apparatus can include a frame having aposterior region for inserting into a mammalian body, an anterior regionopposite the posterior region, and at least one upper cutting elementhaving a cutting surface. The apparatus also includes an extendable bodyoperably coupled to the bottom portion, the extendable body having afirst configuration, and a second configuration, in which the apparatushas a greater height in the second configuration than in the firstconfiguration.

In some embodiments, the extendable body is directly coupled to thehousing, while in others the extendable body is at least partiallyreceived within the housing. Some extendable bodies include a bellows.The bellows can include inward and/or outward folds. The extendable bodymay include a balloon or bladder received within an expandable housinghaving a rigid top and bottom and side panels having inward and/oroutward folds. The bladder can be formed of polyethylene terephthalate(PET), nylon, polyethylene (PE), urethane, or other materials. Theextendable body may include at least one leg received into the housing.The extendable body can include an expandable envelope, which may benested within another structure. Some embodiments include at least twonested structures, one at least partially nested within the other. Thenested structures can include nested, telescoping structures. Thecutting element having the extendable body can include a cutting elementselected from the group consisting of cutting cylinders, cutting belts,and reciprocating cutting planar surfaces.

A shaver cartridge apparatus is also provided by the present invention.The apparatus can include a frame having a posterior region forinserting into a mammalian body, an anterior region opposite theposterior region, and a removable cartridge. The removable cartridge canhave an upper surface bearing a plurality of cutting elements, with thecartridge slidably coupled to the frame to allow for movement of thecutting elements with respect to the frame, and a drive member operablycoupled to the cartridge so as to reciprocatingly drive the cartridge,where the drive member is accessible from outside of the frame. In someembodiments, the drive member is rotatably coupled to an off-center cam,where the off-center cam reciprocatingly drives the removable cartridge.The apparatus can have a protected, non-cutting posterior end region forprotecting tissue.

The present invention also provides an apparatus for simultaneouslycutting into two or more distinct regions of mammalian bone. Theapparatus can include a first frame having a posterior region forinserting into a mammalian body and an anterior region opposite theposterior region, and a second frame having a posterior region forinserting into a mammalian body and an anterior region opposite theposterior region. The first and second frames can have a first andsecond respective moveable cutting body including a an upper cuttingsurface capable of cutting into tissue and bone. The apparatus caninclude a first drive member operably coupled to the first cutting body,a second drive member operably coupled to the second cutting body, andat least one connecting member for maintaining the first and secondframes in spaced apart relation to each other.

In some embodiments, the first and second moveable cutting bodies areeach a rotating cylinder having cutting surfaces, while in otherembodiments the first and second moveable cutting bodies arereciprocating cutting surfaces each bearing cutting elements. In stillother embodiments, the first and second moveable cutting bodies are eachclosed loop belts bearing cutting elements, wherein the belts are drivenby the drive members to move in a longitudinal direction.

Various other aspects are provided by the present invention, in variousembodiments. Some devices are driven by a flexible drive belt that is acontinuous loop. Some cutting surfaces have cutting teeth or abrasivematerial. Some cutters can expand in height using telescoping platforms.Guide posts may be used in some embodiments. The height expansion can beaccomplished with a mechanical cam, screw mechanism, scissors jack, or abladder. This may be via hydraulics in a bladder or in apiston/cylinder, via mechanical scissors, via mechanical cam, or via aspacer or shim. A stand alone telescoping or otherwise extendablesection is used in some embodiments, which can be placed below or withina cutter body.

The present invention also provides an apparatus for cutting into two ormore distinct regions of mammalian bone. The apparatus can include anexpandable apparatus for cutting into mammalian bone, where theapparatus can include a frame having a posterior region for insertinginto a mammalian body, an anterior region opposite the posterior region,and at least one upper cutting element having a cutting surface, and astand alone telescoping or otherwise extendable apparatus having aposterior region for inserting into a mammalian body, an anterior regionopposite the posterior region, and at least one extendable body. Thecutting apparatus is placed in a first distinct region of mammalianbone. The telescoping section is placed in a second distinct region ofmammalian bone. The apparatus can include a drive member operablycoupled to the cutting apparatus, and optionally at least one connectingmember for maintaining the cutting apparatus in spaced apart relation tothe telescoping apparatus. In some embodiments, the telescoping sectionincludes one or more extendable bodies. The telescoping section can havean extendable body directly coupled to the housing, while in others theextendable body is at least partially received within the housing. Theextendable body having a first configuration, and a secondconfiguration, in which the apparatus has a greater height in the secondconfiguration than in the first configuration.

Some cutters are made primarily from stainless steel. The frame andhousing can be made of suitable plastics, such as Polyetheretherketone(PEEK).

Unless otherwise noted, some embodiments of the barrel cutter,reciprocating, and belt cutter devices according to the presentinvention can have a frame length of between about 10 mm and 90 mm, anda width of between about 10 mm and 50 mm. Others have a frame length ofbetween about 10 mm and 90 mm, and a width of between about 40 mm and100 mm. Still others may have a frame length of less than about 10 cmand a width of less than 10 cm. Yet others may have a frame length ofless than about 2 cm and a width of less than about 1 cm.

Unless otherwise noted, some embodiments of the barrel cutter,reciprocating, and belt cutter devices according to the presentinvention can be used by operating two or more cutters at the same time.One cutter can be placed in the medial tibiofemoral compartment and oneplaced in the lateral tibiofemoral compartment. One cutter may be placedin the patellofemoral compartment as well. Any combination of these maybe used. The cutters may have a common drive member, or they may haveindividual drive members. They can be distracted independently, or bedistracted (i.e. deployed) as a set. Each may be deployed under “load”control or under “displacement” control, or a combination thereof. Eachmay be initially deployed under “load” control, then changed to“displacement” control, or visa versa. As they deploy, the frame mayconstrain the cutting elements in a plane parallel to the base of theframe, or allow the plane of the cutting elements to angulate relativeto the base of the frame.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a barrel cutter having transverselymounted rotatable cylindrical cutting elements, irrigation ports, and adrive shaft.

FIG. 2 is a perspective view of a cylindrical cutting element having acentral drive recess suitable for use in some string driven barrelcutters, for example, that of FIG. 12.

FIG. 3 is a perspective view of another cylindrical cutting elementsuitable for use in some end driven barrel cutters, for example, that ofFIG. 1.

FIG. 4 is a perspective view of a reciprocating cutter having an upper,substantially planar cutting element.

FIG. 5 is an exploded view of the reciprocating cutter of FIG. 4,showing the irrigation ports and the reciprocating drive shaftmechanism.

FIG. 6 is a perspective view of the barrel cutter of FIG. 1.

FIG. 7 is a top, cross-sectional view, taken through the cutting elementcenters, of the barrel cutter of FIG. 1, showing the bevel gear drivefor driving the barrel cutters.

FIG. 8 is a side, cross-sectional view, taken though the drive gears, ofthe barrel cutter of FIG. 1, showing the end driven cutter elements andgear drive train.

FIG. 9 is a top, schematic view of the barrel cutter of FIG. 1.

FIG. 10 is a side, elevation view of the barrel cutter of FIG. 1.

FIG. 11 is an exploded view of the barrel cutter of FIG. 1.

FIG. 12 is a perspective view of a string driven barrel cutter having abottom telescoping platform, a side drive shaft, and which can use thecutter element of FIG. 2.

FIG. 13 is a side, cross-sectional view of the string driven barrelcutter of FIG. 12, taken through the drive loop.

FIG. 14 is an exploded view of the string driven barrel cutter of FIG.12.

FIG. 15 is a perspective view of the string driven barrel cutter of FIG.12, shown in a collapsed configuration.

FIG. 16 is a side, cross-sectional view of the string driven barrelcutter of FIG. 12, taken through the drive loop, shown in an expandedtelescope configuration.

FIG. 17 is an exploded view of the string driven barrel cutter of FIG.12, with the telescoping platforms shown in an expanded, configuration.

FIG. 18 is a perspective view of a belt cutter having a lineartensioning frame using a screw mechanism to tension the cutting belt.

FIG. 19 is an exploded view of the belt cutter of FIG. 18 having alinear tensioning frame.

FIG. 20 is an exploded view of another belt cutter, having a hingetensioning frame using a scissors mechanism to tension the cutting belt.

FIG. 21 is a perspective view of a reciprocating cutter having asubstantially planar upper cutting element and a side drive shaft.

FIG. 22 is an exploded view of the reciprocating cutter of FIG. 21,showing irrigation ports and plenum, and an off-set cam reciprocatingmechanism within.

FIG. 23 is perspective view of an expandable telescoping bladder, shownin a collapsed configuration.

FIG. 24 is a perspective view of an expandable housing, suitable forreceiving the bladder of FIG. 23 within.

FIG. 25 is a perspective, cutaway view, and a non-cutaway view, of thebladder of FIG. 23 disposed within the platform of FIG. 24, shown in acollapsed configuration.

FIG. 26 is a perspective, cutaway view, and a non-cutaway view, of thebladder of FIG. 23 disposed within the platform of FIG. 24, shown in anexpanded configuration.

FIG. 27 is a perspective view of a dual belt cutter positioned in theknee joint.

FIG. 28 is a perspective view of a belt cutter.

FIG. 29 is a perspective view of a knee joint with the tibial plateausresected.

FIG. 30 is a lateral side view of the knee with a telescoping cutterpositioned in the lateral tibiofemoral joint.

FIG. 31 is a medial side view of the knee with a telescoping cutterpositioned in the medial tibiofemoral joint.

FIG. 32 is lateral side view of the knee with a telescoping cutterpositioned in the patellofemoral joint.

FIG. 33 is a schematic top view of a reciprocating drive top cuttingelement and drive shaft.

FIG. 34 is a perspective view of dual barrel cutters, which can besimilar to the barrel cutters of FIG. 12, shown in position in thetibiofemoral compartments.

FIG. 35 is a perspective view of dual barrel cutters, for example thebarrel cutters of FIG. 12.

FIG. 36 is a perspective view of dual reciprocating cutters shown inposition in the tibiofemoral compartments.

FIG. 37 is a perspective view of dual barrel cutters positioned in theknee joint.

FIG. 38 is a perspective view of dual belt cutters, for example the beltcutters of FIG. 20, shown in position in the tibiofemoral compartments.

FIG. 39 is a perspective view of dual belt cutters, for example the beltcutters of FIG. 20.

FIG. 40 is an end elevation view of a reciprocating cutter, having thetelescoping platform in an extended configuration.

FIG. 41 is an end elevation view of the reciprocating cutter of FIG. 40,having the telescoping platform in a retracted or collapsedconfiguration.

FIG. 42 is an exploded view of the reciprocating cutter of FIG. 40,showing the retainer for securing the top cutting element.

FIG. 43 includes orthogonal views and a perspective view of a cuttingbelt.

FIG. 44 includes orthogonal views of a cutting belt.

FIG. 45 includes orthogonal views of a cutting belt.

FIG. 46 includes orthogonal views of a cutting belt.

FIG. 47 includes perspective views of a cartridge for use in removingbone.

FIG. 48 includes exploded views of the cartridge of FIG. 47.

DETAILED DESCRIPTION OF THE INVENTION

Some embodiments of the invention include replacing the articulatingsurfaces of the knee with implants. Supporting information is includedin current patents and patent applications, to include U.S. Pat. No.6,482,209 and U.S. Pat. No. 6,723,102, herein incorporated by reference.

The present application includes disclosure of bone-sculpting tools forpreparing the femoral condyles and trochlea. Sculpting instruments,sculpting instrumentation, sculpting devices, sculpting apparatus andbone-sculpting tools are interchangeable terms. It should be noted thattissue guided surgery and the sculpting device embodiments areapplicable to other joints in the body, to include but not limited tothe hip, shoulder, ankle; and motion segments of the spine, to includethe disc and facet joints. The femoral cutter (sculpting devices)described herein include a shaver (as initially described in U.S. Pat.No. 6,428,209), a barrel cutter, a reciprocating cutter and a beltcutter. Various embodiments of each are presented.

FIG. 1 illustrates a barrel cutter designed with multiple cylindricalcutting elements 103. The barrel cutter can be designed with one or morecutting elements 103. In one embodiment the barrel cutter is designedwith five cutting elements 200 (as shown in FIG. 12).

The area of contact between the bony surfaces of the tibiofemoral andpatellofemoral compartments moves along the surface of the femur, withineach compartment, as the knee flexes and extends. This movement isgreater on the lateral side due to rotation of the tibia. Hence, it isdesirable to have a cutting surface sized to remove bone as the locationof the contact area moves over the surface of the femur. In oneembodiment the cutting elements 103 are small in diameter and spacedclosely together. The overall cutting surface area as shown in FIG. 1has a cutting surface length 108, a cutting surface width 109, and issized to accommodate the movement of the medial or lateral tibiofemoralcontact area during knee flexion and extension and the width of themedial or lateral femoral condyle. In general, in some embodiments, thecutting surface length may range from approximately 10 mm to 90 mm andthe cutting surface width may range from 10 mm to 50 mm, for cuttersdesigned to be placed in either tibiofemoral compartment. In anotherembodiment in which the tibial plateau is resected, the cutting surfacewidth matches that of the mediolateral width of the distal femur, whichmay range from approximately 40 mm to 100 mm.

FIGS. 1, 6, 7, 8, 9 and 10, illustrate one embodiment of a barrelcutter, in which the cutting elements 103 are supported by a cutterhousing 107 and a side plate 102. Cutter housing 107 is separated fromdrive housing 101 by spacer plate 111, and from side plate 102 by spacerplate 110. Side plate 102 can be secured using fasteners 1000 (shown inFIG. 10). Side plate 102 can also include top attachment holes 900(shown in FIG. 9). Optionally, two barrel cutters can be usedsimultaneously to prepare the medial and lateral femoral condyles. In aleft knee the shown barrel cutter is placed in the medial tibiofemoralcompartment. A barrel cutter (not shown) structured as the mirror imageof the barrel cutter shown is placed in the lateral tibiofemoralcompartment. Each barrel cutter structured with four attachment holes900 to which a cross bar (not shown) can be attached with threadedfasteners (not shown) to stabilize and orient one barrel cutter to theother. Alternatively, each barrel cutter can be placed in respectivetibiofemoral compartments independently without connecting themtogether.

The drive housing 101 supports a drive shaft 100. A rigid or flexibledrive shaft extension (not shown) can be attached between the driveshaft 100 and a rotational power supply, such as a surgical power drillor a motor. FIG. 7 illustrates how input torque can be delivered todrive shaft 100 which is attached to a bevel gear set 700 and 701 (orbevel gears 1100 and 1101 in FIG. 11). FIG. 8 illustrates how torque istransferred to drive gear 805 by shaft 702. From the cutter drive gear800, torque is transferred to a transfer gear 804 to a cutter drive gear800. Idler gears 803 are placed between subsequent cutter drive gears800 to transfer torque to each of the cutting elements 103. A lock pin802 is placed into gear relief 801 and relief 303 to secure the gear tothe cutter. In one embodiment, the cutter drive gears 800 are pinned tothe cutter hub 302 (shown in FIG. 3). Referring to FIGS. 8 and 11, thebarrel cutter is structured to drive cutting elements 103 with driveshaft 100 connected to bevel gear 1100. Bevel gear 1100 meshed withbevel gear 1101 which is connected to shaft 1105 which is connected todrive gear 805 which meshes with transfer gear 804. Transfer gear 804meshes with cutter drive gear 800 which meshes with idler gear 803 andtorque is transferred to each cutting element via idler gear 803 anddrive gear 800 combinations. Transfer gear 804 and idler gears 803 aresupported by shafts 1109. Shafts 1109 passing through and supported byclearance hole 1114 in side plate 102 and clearance hole 1115 in faceplate 1102. Face plate 102 is assembled with cutter housing 107 bythreaded fasteners (not shown) passing through clearance holes 1116 inside plate 102, clearance holes 1117 in face plate 1102 and intothreaded holes 1106 in cutter housing 107.

FIG. 3 illustrates that cutting element 103 has one or more cuttingedges 106, and in one embodiment there are four cutting edges 106 asshown in FIG. 3. Cutting element 103 is supported on one end by a hub301 and at the other end by a gear hub 302. A cutter relief 300 isdesigned trailing the cutting edge 106 to enhance cutting.

FIGS. 1, 6 and 11 illustrate features which beneficially flush bonedebris out of the femoral cutter during operation. Sterile saline orother suitable fluid may be used for this purpose. The barrel cutter isdesigned with input port 104 and output port 105. Irrigation fluid isdelivered to the barrel cutter by a plastic tube (not shown) structuredto attach to the barrel cutter at port 104 to be channeled throughhousing 101, through face plate 1103 via irrigation input port 1107,into channel 1104 leading to longitudinal hole 1111 in communicationwith each cutting element 103 relief channel 1112. Irrigation fluidflows over cutting element 103 to be gathered in longitudinal hole 1113in communication therewith. Irrigation fluid flowing through face plate1103 via irrigation output port 1108 in communication with port 105 inhousing 101 and into a plastic tube (not shown) structured to attach tohousing 101.

Durability, sharpness and cleanability are important for the functionand use of the femoral cutter. Given the small size of the femoralcutters, a single use device is preferred to provide sharp cuttingelements in each surgical case and to ensure durability of the device.Cost is an important factor in single use devices. The use of gears todrive the cutting elements is costly for two reasons, the cost of thegears and the cost of machining to hold tolerances for proper functionof the gears. Hence, a less expensive drive means would be desirable.

FIG. 13 illustrates another embodiment of a barrel cutter, in which astring drive is used to drive each of the cutting elements. The stringdrive can be a continuous loop that is wrapped around each cutter andaround an input shaft so that as the input shaft is rotated, eachcutting element rotates. The string drive is designed with a drive loop1300, which may be a monofilament string, multi-strand woven string orcord; single or multi-strand wire; drive belt, V-belt or timing belt; orother flexible band that can be placed around or on the cutting elementsto impart rotation. The drive loop 1300 is wrapped around a drive shaft1202 one time as shown, or in another embodiment multiple times (notshown) to take advantage of the increased friction between the driveloop and shaft with multiple windings. The drive loop 1300 can bewrapped one or more times around each cutting element 200.

FIG. 2 illustrates a cutting element 200 designed with a recess 203 forreceiving drive loop 1300. The cutting element can be supported by hubs201. Cutting element 200 includes cutting edges 202, and chip relief204, formed as a circumferential groove in this embodiment. Cuttingelement 200 is structured with one or more cutting edges 202. Eachcutting edge 202 is structured with one or more chip relief's 204 thatimprove cutting element's 200 chopping of articular cartilage present onthe femoral condyle and in chopping bone to be removed. FIGS. 12, 13 and14 illustrate an embodiment in which the string drive is integral to thefemoral cutter. Drive shaft 1202 and cutting elements 200 are supportedby a common housing 1200 and 1201, and a means for tensioning the loopdrive 1300 is provided. Common housings 1200 and 1201 are held inalignment by alignment pins 1301 slidably received in holes 1400. Commonhousings 1200 and 1201 structured to be adhesively bonded togetherbetween common faces 1404 and 1405. In another embodiment (not shown)the drive shaft is supported in a separate housing and one or twoflexible tubes connect the drive shaft housing to the cutting elementhousing. In an embodiment using one flexible tube the dive loop iswrapped around the drive shaft one or more times and passed through theflexible tube into the cutter housing wherein the loop drive is wrappedone or more times around each cutting element. In an embodiment usingtwo flexible tubes, the drive loop would be an open loop in which thestring is passed through one tube, into the cutting element housing,wrapped one or more times around each cutting element, routed out of thecutting element housing, through the second tube, into the drive shafthousing, then wrapped one or times around the drive shaft and connectedto the other end of the drive loop. Alternatively, for the single ordual tube embodiments, the flexible tube may be rigid and made of steel,plastic or other suitable material.

FIG. 14 illustrates an embodiment in which drive shaft 1202 is designedwith ridges 1401 and 1402 and a groove 1403 to guide drive loop 1300.The opposing faces 1404 and 1405 of the housing can be brought togetherover alignment pins 1301 inserted into holes 1400.

As described above, it is beneficial to expand the cutters within thepatellofemoral compartment and tibiofemoral compartments. The barrelcutter is designed with a cylinder to provide axial expansion of thecutter. FIG. 13 illustrates that the cylinder may be of multiple stagesas shown by telescoping platforms 1302, 1303 and 1304, which are held inplace within housing 1200 and 1201 with telescoping platform 1203. FIG.13 shows the cylinder in a collapsed position. FIGS. 15, 16 and 17 showthe cylinder in an extended position.

FIGS. 4 and 5 illustrate a reciprocating cutter designed to be placed ineither the tibiofemoral compartment and/or in the patellofemoralcompartment. Cutting element 400 is designed with cutting teeth on topsurface 500. The cutting teeth may be continuous from side to side orinclude individual cutters staggered over the surface of the cuttingelement so as to provide uniform material removal over the surface ofthe cutting element. Alternatively, the top surface may have an abrasivetexture to remove material. In either case, the surface of the cuttingelement may be continuous or may have holes to allow material removedfrom the femur to pass through.

Cutting element 400 is driven in a reciprocating fashion by applyingtorque to drive shaft 404. Torque may be supplied by a surgical powerdrill or a motor. A flexible or solid drive shaft can be used to connectthe surgical power drill or motor to drive shaft 404. A reciprocatingdrive groove 506 is formed by an upper boss 505 and a lower boss 504,and having an upper groove wall 507 and a lower groove wall 508. As thedrive shaft spins, reciprocating drive groove 506 imparts areciprocating motion to cutting element 400. A hub 502 rides withinreciprocating drive groove 506 and moves in an axial direction to drivecutting element 400 via cutter arm 501. Drive shaft 404 includes an endhub 509 which is received in hub support 511 adjacent a reciprocatingdrive recess 510 and a drive shaft recess 512. Distal end of drive shaft404 is structured with hub 509 to align and support distal end of driveshaft 404. Drive shaft 404 is supported in drive housing 402 and drivecover 401 each structured with hub support 511 to support distal end ofdrive shaft 404 and drive shaft support 512 to support drive shaft 404.Clearance for lower boss 504 and upper boss 505 within drive housing 402and drive cover 401 is provided by recess 510. FIG. 33 illustrates thatcam 3302 rides in the groove 3306 between bosses 3304 and 3305 whiledrive shaft 3303 rotates, resulting in a reciprocating motion of arm3301 and cutting element 3300. Cutting element 400 is supported by drivehousing 402. Drive shaft 404 and cutter arm 501 are held in relativeposition by drive housing 402 and enclosed by drive cover 401.

FIGS. 40, 41, and 42 show that as cutting element 400 reciprocates, theposterior aspect of the cutting element 400 is beneficially guided andcutting element 400 is retained on the surface of the drive housing 402.A retainer 4000 is visible on the underside of cutting element 400. Theretainer 4000 fits into cavity 4200 and is held vertically by a shoulder4201 fitting into a groove 4202. The cavity is elongated to allowreciprocating motion of the cutter element 400.

FIGS. 21 and 22 illustrate an alternate embodiment having a cuttingelement 2100 structured to be supported on housing base 2101. Saidhousing 2101 base structured to support drive shaft 2104 and enclosesaid drive shaft 2104 with housing cap 2103. Drive shaft 2104 structuredto oscillate cutting element 2100. Off set cam 2200 is in communicationwith channel 2205 in cutting element 2100 arm 2206. Housing base 2101 isstructured with chamber 2214 to provide clearance for drive shaft 2104bosses 2201 and 2202. Drive shaft 2104 cylinder 2204 is slidablyreceived in channel 2203 in housing base and in adjoining channel (notshown) in housing cap 2103. Bosses 2201 and 2202 capture said channel2203 to slidably retain drive shaft 2104. As drive shaft 2104 rotates,cam 2200 rotates and slides within channel 2104 thereby moving cuttingelement back and forth within bosses 2215 protruding from housing base2101. Cutting surface 2207 structured to remove tissue when oscillatedagainst adjoining bone. Cutting surface structure includes embodimentsdescribed here in, to include ridges, grit surface, protuberances, orother suitable cutting feature known to those skilled in the art.Reciprocating cutter is structured to telescope. Telescoping platform2102 is structured to slidably assemble with housing base 2101. Guideposts 2208 are slidably received in holes 2210. The leading end of guideposts 2208 are structured with snap retainers 2209 that engage lips 2216within holes 2210. Tissue removed from the femur flows into chamber2211. Input hole 2212 is structured to attachably receive a tube (notshown) through which irrigation fluid flows into chamber 2211.Irrigation fluid is transported out of chamber 2211 through output hole2213. Said output hole 2213 structure to attachably receive a tube (notshown) which may be connected to a vacuum system (not shown).

FIG. 5 illustrates that a port 515 brings irrigation fluid, e.g. sterilesaline, into a cavity 514 behind cutting element 400 via opening 518.The fluid exits the cavity via opening 519 and port 516. As mentionedearlier, it is beneficial to wash debris from femoral resections awayfrom the cutter.

FIGS. 4 and 5 illustrate a reciprocating cutter which can expand. Atelescoping platform 403 is provided on the base of the cutter. Guideposts 503 align the telescoping platform 403 and limit travel by snap-inretainers 517. Guide posts 503 are designed to fit into and snap intoreceiving holes 513 in the drive housing 402.

FIG. 41 illustrates the reciprocating cutter in a fully collapsedposition. The collapsed reciprocating cutter fits easily into atibiofemoral compartment, or into the patellofemoral compartment. Totension the ligaments and capsule the reciprocating cutter can beexpanded as shown in FIG. 40. Expansion of the telescoping platform maybe accomplished by a mechanical cam, screw mechanism or scissors jack(not shown), or by a bladder. Bladder designs are described below.

FIG. 18 illustrates yet another embodiment, a femoral cutter having acutting belt 1800. Cutting belt 1800 is supported on a frame and drivento move the cutting surface across the adjacent femoral condyle ortrochlea. Cutting belt 1800 can be tensioned and supported on rollers.Torque is applied to the drive shaft 1803 by a surgical drill or motorwith a flexible or rigid drive shaft as previously described. As thebelt cutter is placed into a tibiofemoral compartment and operated, thetissue structures in the back of the knee need to be protected. A tissueprotector 1804 is designed as part of the housing base 1801 for thispurpose. A housing end cap 1805 may be seen at the anterior end.

FIG. 19 illustrates the femoral cutter of FIG. 18 in an exploded view.Cutting belt 1800 is supported on an idler roller 1906 having a shaft1907 received within, and a drive roller 1903 having a drive shaftcylinder 1904 received within. Hole 1922 through idler roller 1906snuggly receives shaft 1907 structured to press fit shaft 1907 in hole1922. Tensioning arm 1900 is structured with tabs 1916 protruding fromdistal end through which holes 1913 pass. Idler roller 1906 ispositioned between tabs 1916 and shaft 1907 is slidably received throughfirst hole 1913, press fit through hole 1922 in idler roller 1906, andslidably received in second hole 1913. As for the drive roller 1903,housing frame 1802 and housing end cap 1805 adjoin along interface 1807.Hole 1912 extends along interface 1807 and slidably receives drive shaft1803. Hole 1905 through drive roller 1903 snuggly receives drive shaft1803 structured to press fit drive shaft 1803 in hole 1905. Drive shaft1803 is press fit into hole 1905. Boss 1915 protruding from housingframe 1802 is slidably received in channel 1914 in housing frame 1802.Screws 1908 are assembled in threaded holes 1909 in housing frame 1802.Assembled drive roller 1903 and drive shaft 1803 are slidably receivedby the portion of hole 1912 formed in housing frame 1802. Skid 1902 isplaced on said assembly and the combination placed inside cutting belt1800 with said cutting belt positioned between bosses 1808 protrudingfrom housing frame 1802. Screws 1908 are advanced to properly tensioncutting belt 1800. Drive shaft 1803 is secured by the portion of hole1912 formed in housing end cap 1804. Housing end cap 1804 is assembledto housing frame with threaded fasteners (not shown) slidably receivedthrough holes 1917 and threaded into receiving holes (not shown) inhousing frame 1802. Skid 1901 is placed inside housing base 1801 andcombination is placed onto assembled cutting belt 1800, housing frame1802 and housing end cap 1805. Housing base 1801 is assembled totensioning arm 1900 with threaded fasteners (not shown) slidablyreceived through holes 1919 in tabs 1918 protruding from housing base1801. Said screws treadably received in threaded holes 1920 intensioning arm 1900. Hole 1921 in housing frame 1802 is structured toattachably receive a plastic tube to which operating room suction isapplied to remove fluid and tissue debris from tissue and bone cutting.

As the cutting surface 1806 of cutting belt 1800 works against thefemoral condyle or trochlea, compressive force is carried by a skid 1902below the belt and structural support is provided to the frame by asecond skid 1901. Tissue is removed by one or more protuberances 1923structured in the cutting belt 1800. Such protuberances 1923 formed bystamping or pressing a form into cutting belt 1800, or by attaching aformed or machined protuberance to the cutting belt 1800. Suchattachment by adhesive, welding, diffusion bonding, press fit or otherattachable means know in the art. Cutting belt 1800 is fabricated fromstainless steel, cobalt chromium molybdenum alloy, or other suitablemetal. Alternatively, cutting belt 1800 may be fabricated from rubber,urethane, or other suitable polymeric material with embeddedprotuberances as described above. Optionally, said polymeric cuttingbelt may be reinforced by fibers, metal mesh or other suitable materialto increase strength and durability. A polymeric cutting belt can haveintegral metal cutting elements with protuberances. Alternatively, themetal cutting elements can be abrasive. To tension the cutting belt1800, the housing frame 1802 is adjustable by turning two screws 1908 toadvance a tensioning arm 1900 to increase tension on the belt cutter.The belt is driven in the direction shown in FIG. 19 by applying torqueto the drive shaft 1803 which is attached to the drive roller 1903. Thebelt slides across upper skid 1902 and lower skid 1901, and turns on anidler roller 1906. A surgical drill, or a motor, with a flexible driveshaft as previously described can be used to apply torque to the driveshaft 1803.

To remove material from the femur, the cutting belt 1800 is designedwith holes 1910 that create a rough edge when run against the femur.Alternately, the trailing edge 1911 of the hole 1800 is elevated to forma grater for more aggressive cartilage and bone removal (see the beltdetail in FIG. 19). The cutting belt is formed by cutting or stampingthe hole pattern in a strip of metal or other suitable material andwelding or bonding the ends together to form a belt. Alternatively, theouter surface of belt 1800 can be abrasive.

FIGS. 43, 44 and 45 illustrate alternate cutting belt embodimentsfabricated from a strip that is welded or bonded (e.g. at 5307) into abelt or loop. In an alternate embodiment, a cutting pattern ischemically etched, stamped or machined into the outer surface of thecutting belt. As shown in FIG. 43, ridges 5302 are formed into the outersurface 5300 of the cutting belt. The outer ridge pattern 5302 isperpendicular to the side 5303 of the belt. The inner surface 5301 mayhave a pattern chemically etched, stamped or machined in it to enhancetraction with the drive roller described above, or the inner surface maybe smooth or roughened. The inner ridge pattern 5304 is perpendicular tothe side 5303 of the belt. The belt is formed into a loop and thefastening edges 5305 and 5306 are welded or bonded together.

FIG. 44 shows an alternate embodiment, in which a cutting pattern ischemically etched, stamped or machined into the outer surface of thecutting belt. Ridges 5402 are formed into the outer surface 5400 of thecutting belt. The outer ridge pattern 5402 is inclined relative to theside 5403 of the belt. The inner surface 5401 may have a patternchemically etched, stamped or machined in it to enhance traction withthe drive roller described above, or the inner surface may be smooth orroughened. The inner ridge pattern 5404 is inclined relative to the side5403 of the belt. The belt is formed into a loop and the fastening edges5405 and 5406 are welded or bonded together.

FIG. 45 shows an alternate embodiment belt having a side 5503, in whichbelt a cutting pattern is chemically etched, stamped or machined intothe outer surface of the cutting belt. Alternatively, the outer surfaceof belt can be abrasive. Abrasive surface, as used herein, formed bygrit blasting, plasma spray, bonding abrasive material, or otherfabrication method known to one skilled in the art. Ridges 5502 areformed into the outer surface 5500 of the cutting belt. The outer ridgepattern 5502 is alternating, opposing, inclined ridges partiallyspanning the belt. The inner surface 5501 may have a pattern chemicallyetched, stamped or machined in it to enhance traction with the driveroller described above, or the inner surface may be smooth or roughened.The inner ridge pattern 5504 is a diamond pattern. The belt is formedinto a loop and the fastening edges 5505 and 5506 are welded or bondedtogether.

FIG. 46 illustrates yet another embodiment, in which the cutting belt5605 is made from a deep drawn can 5600. A right cylinder is formed bydeep drawing stainless steel or other suitable material. The can 5600 isopen on one end 5601 and closed on the other 5603. The closed end of thecan is removed along cut line 5602 forming a continuous belt 5604 intowhich the patterns described above can be chemically etched, machined orstamped. For example, perpendicular ridges 5607 are chemically etched,stamped or machined into the outer surface of the cutting belt 5605. Fortraction with the drive roller a ridge pattern may be formed into theinner surface of the belt. A perpendicular ridge pattern 5606 on theinner surface is shown in FIG. 46. It should be noted that the outer andinner surface patterns described above can be used in any combinationand that holes through the belt as previously described can be added.

FIG. 20 illustrates an alternate embodiment belt cutter in which theframe and tensioning mechanism uses a hinged frame. In this embodiment,the anterior tensioning frame 2001 having support face 205 and hole 204,and the posterior tensioning frame 2002 are initially pinned togetherwith one pin 2007 to form a hinge. Pin 2007 is slidably received throughfirst hole 2010 then press fit through hole 2014 then slidably receivedin second hole 2010. The tensioning frame 2001 and 2002 support driveroller 2003 that is press fit or attached to drive shaft 2006 receivedwithin a drive roller 2003, and an idler roller 2004 rotating on a shaft2005. Idler roller 2004 is placed between tabs 2021 protruding fromposterior tensioning frame 2002. Shaft 2005 is slidably received throughfirst hole 2020 and press fit through hole 2018 in idler roller 2004then slidably received in second hole 2020. Drive roller 2003 is placedbetween tabs 2022. Drive shaft 2006 is slidably received through firsthole 2019 and press fit through hole 2017 in drive roller 2003 thenslidably received in second hole 2019. The tensioning frame is angledabout the pivot pin 2007 to allow placing the tensioning frame into thecutting belt 2000. Once in place, the tensioning frame is opened into astraight position aligning the anterior and posterior tensioning frames,2001 and 2002, respectively. The tensioning frame is held in thisposition by placing locking pin 2012 into a receiving hole 2013 in theposterior tensioning frame 2002 that is now aligned with a receivinghole 2011 in the anterior tensioning frame 2001. Pin 2012 is slidablyreceived through first hole 2013 then press fit through hole 2011 theslidably received in second hole 2013. The assembled tensioning frameincludes a distal tissue protector 2009, and a cutting belt which issupported in a housing base 2008 having a support face 2016. Supportfaces 2016 of housing base 2008 are structured to snap fit on to tensionframe assembly at adjoining support faces 2015 on anterior tensioningframe 2001.

FIG. 28 illustrates another embodiment in which the belt cutter 2801,having frame 2800, drive shaft 2803, and shaft 2804, has the cuttingteeth 2802 directed posteriorly, so as to force the femur posteriorlywhile cutting.

FIG. 29 illustrates how the tibial plateau can be prepared by resectingthe articular surfaces leaving lateral support surface 2902 and medialsupport surface 2903 on which tissue guided femoral cutters are placedto prepare the adjacent femoral condyles. The medial 2903 and lateral2902 support surfaces may be prepared at the same time thereby allowingsimultaneous preparation of medial and lateral femoral condyles.Optionally, either medial 2903 or lateral 2902 support surface may beprepared initially followed by preparation of the adjacent femoralcondyle. A spacer may be placed in the prepared tibiofemoral compartmentfollowed by preparation of the adjacent tibial support surface followedby preparation of the adjacent femoral condyle. The medial and lateraltibial articular surfaces may be resected independently as shown in FIG.29 in which case the tibial eminence 2907 is preserved. Alternatively,the anterior portion of the tibial eminence 2907 may be resected toallow for a bridge or connection between the medial and lateral tibialimplants, or the tibial eminence 2907 may be resected. The medial andlateral tibial resections may be co-planar. Alternatively, the medialand lateral resection may be parallel, but not co-planar. In yet anotherembodiment the medial and lateral tibial resection may not be co-planarnor parallel. The femoral condyles may be resected independently,simultaneously, or in combination with the femoral trochlea. In oneembodiment the femoral cutters telescope to distract the joint; eitherone or both of the tibiofemoral compartments and/or the patellofemoralcompartment. Such distraction can be performed under constant load.Alternatively, such distraction may be at discrete displacement steps ordistracted to a desirable displacement for condyle(s) and/or trochlearesection. Femoral condyle preparation is guided by the kinematics ofthe knee joint. The tibia 2901 moves in a predetermined fashion aboutthe femur 2900. This motion is determined by the soft tissue structuresspanning the knee. The anterior cruciate ligament (ACL) 2905 and theposterior cruciate ligament (PCL) 2907 extend from the femoralintracondylar notch to the tibial eminence 2908. The medial collateralligament (MCL) 2906 extends from the medial side of the femur to themedial side of the tibia. The lateral collateral ligament (LCL) 2904extends from the lateral side of the femur to the lateral side of thetibia. The ACL 2905, PCL 2907, MCL 2906 and LCL 2904 are the primaryligamentus structures guiding motion of the tibia relative to the femur.

In tissue guided surgery a femoral cutter may be placed in eachtibiofemoral compartment and in the patellofemoral compartment. Thecutting elements are held against the femur while the knee is flexed andextended in order to remove bone from the femur to prepare supportsurfaces for trochlear and/or condylar implants. Initially, it isbeneficial to tension the ligaments spanning the knee and the jointcapsule to stabilize the joint with the cutters in place and to provideuniform kinematic motion. As bone is removed it is beneficial to expandthe cutters to maintain tension on the ligaments spanning the knee andthe joint capsule. The cutters may be expanded incrementally to discreteheights, or variably under constant distraction force. In the firstcase, which is referred to as “displacement control,” spacers may beplaced under the cutters to expand the cutter, or a hydraulic cylinderwith incremental fluid filling may be designed into the cutter to expandthe cutter, in the patellofemoral compartment or in either of thetibiofemoral compartments. In the second case, which is referred to as“load control,” a hydraulic cylinder, or a bladder, with pressurecontrolled fluid filling may be designed into the cutter to expand thecutter in the patellofemoral compartment or in the either of thetibiofemoral compartments.

FIGS. 30, 31 and 32 illustrate that the medial and lateral femoralcondyles may be prepared independently with a femoral cutter 3002,placed in the lateral tibiofemoral compartment first to prepare thelateral femoral condyle. A spacer is placed in the lateral tibiofemoralcompartment (not shown) after preparation of the lateral condyle, andthe procedure is repeated by placing a femoral cutter 3102 in the medialtibiofemoral compartment. A bladder 3003 or 3103 may be used inconjunction with the lateral or medial femoral cutter, respectively.

FIG. 32 illustrates that the femoral trochlea may be prepared by placinga femoral cutter 3202 on the patella. The cutter can be structured toprepare a linear surface generally in a medial—lateral orientation andcurved in a sagittal plane. Alternately, cutting elements 3206 as shownin inset of FIG. 32, the cutter, structured with various cuttingelements to include barrel cutters, belt cutters, reciprocating cuttersor shavers, may be contoured to simulate the shape of the patellargroove. Telescoping bellows 3203 may be used as well.

FIGS. 34 and 35 illustrate two barrel cutters linked together. Inpreparing the medial and lateral tibiofemoral compartments it may bebeneficial to place femoral cutters in each compartment andsimultaneously prepare the medial and lateral femoral condyles. In thecase of the barrel cutters, the two cutters are linked together with onecutter 3402, having telescoping platform 3406, placed in the lateraltibiofemoral compartment and the other cutter 3403, having telescopingplatform 3405, placed in the medial tibiofemoral compartment. Theconnecting bridge 3404 transfers torque from drive shaft 3407 betweenthe two femoral cutters. Alternately, the two cutters may be poweredindependently. The connecting bridge 3404 may be rigid and of fixedlength or in another embodiment the connecting bridge 3404 is flexibleand telescopes to enable independent positioning of the femoral cutterswithin each tibiofemoral compartment.

FIGS. 36 and 37 illustrate two reciprocating cutters linked together,with one cutter 3602 placed in the lateral tibiofemoral compartment andthe other cutter 3603 placed in the medial tibiofemoral compartment. Theconnecting bridge 3604 transfers torque from drive shaft 3605 betweenthe two femoral cutters. Alternately, the two cutters may be poweredindependently. The connecting bridge 3604 may be rigid and of fixedlength or in a preferred embodiment the connecting bridge 3604 isflexible and telescopes to enable independent positioning of the femoralcutters within each tibiofemoral compartment.

FIGS. 27, 38 and 39 illustrate two belt cutters linked together, to forma dual belt cutter 2707, with one cutter 2702 or 3802 placed in thelateral tibiofemoral compartment (between femurs 2700 or 3600 and tibias2701 or 3601) and the other cutter 2706 or 3803 placed in the medialtibiofemoral compartment. The connecting bridge 2703 or 3804 transferstorque between the two femoral cutters. Alternately, the two cutters maybe powered independently. The connecting bridge 2703 or 3804 may berigid and of fixed length or in a preferred embodiment the connectingbridge 2703 or 3804 is flexible and telescopes to enable independentpositioning of the femoral cutters within each tibiofemoral compartment.A telescoping bladder 2705 may be placed under each belt cutter.

FIG. 23 illustrates a bladder, shown in a collapsed form. As describedabove, it is desirable to extend a femoral cutter once it has beenplaced in either of the tibiofemoral compartments or in thepatellofemoral compartment. In one embodiment a fluid or gas filledbladder is placed under the femoral cutter to extend the bladder—cuttercombination within the joint space. A bladder 2300 as shown in FIG. 23can be made of a suitable material, such as, but not limited to, PET,nylon, polyethylene or urethane. In its collapsed form the bladder 2300is flat and can be filled via a port 2302 and neck 2301 in one end.Alternately, there may be two ports (not shown) to allow air to bleedfrom the bladder as fluid is injected into the bladder. The bladder maybe compliant to enable expansion in all directions once placed between afemoral cutter and the tibia, or between a femoral cutter and patella.Alternatively, the bladder may be non-compliant to constrain bladderexpansion to a designed volume.

In preparing the femoral articular surfaces the femoral cutters mayrequire greater translational stability than what is provided by a freestanding bladder. Such stability can be provided by designing atelescoping device within the cutter as described herein, then placingthe bladder within this telescoping section. In addition, the bladdermay be susceptible to puncture by instruments used in the surgicalprocedure or by the bony support surface. Hence, it may be desirable tohouse the bladder in an expandable platform that can be placed betweenthe femoral cutter and the tibia or the patella.

FIGS. 24, 25 and 26 illustrate an expandable housing which may have anexpandable bladder housed within. The expandable housing may befabricated out of metal, plastic or other suitable material. The topplate 2400 and bottom plate 2401 can be rigid or semi-rigid. Thesidewalls 2402 and 2403 can fold either in on one another or out on oneanother to minimize thickness in a collapsed state (see FIG. 25). Anopening 2404 is provided for the neck 2301 of the bladder.

FIG. 26 illustrates the housing as the bladder within is filled suchthat the expandable housing telescopes to a designed height. If filledwith sterile saline or other suitable fluid that is incompressible theheight of the expandable housing can be incrementally increased ordecreased to facilitate appropriate femoral resection. Alternatively,the fluid can be introduced into the bladder 2300 within the expandablehousing under pressure control in which case the distraction forcewithin the tibiofemoral or patellofemoral compartment can be controlledto facilitate appropriate femoral resection.

FIGS. 47 and 48 illustrate a shaver being placed in a tibiofemoral jointand the knee flexed and extended to move the femoral condyle over thecutting elements of the shaver to remove material from the condyle. Inanother embodiment a reciprocating motion is applied to the shaver toenhance material removal from the condyle while the knee is flexed andextended. As shown in FIGS. 47 and 48, a femoral shaver designed for usein either the medial or lateral tibiofemoral compartments provides aframe 5805 with a flat support surface for support on the preparedtibial plateau. The femoral condyle is sculpted by a set of cuttingelements 5810 integral to a cartridge 5800. Alternately, the cuttingelements 5810 may be designed as an insert that fits into the cartridge5800. A rigid or flexible drive shaft extension (not shown) can beattached between the drive shaft 5802 and a rotational power supply suchas a surgical power drill or a motor.

A reciprocating motion can be applied to the cartridge 5800 to enhancematerial removal from the femoral condyle. The cartridge shown isdesigned to move axially in a channel 5813 within the frame 5805. In oneembodiment a drive cam 5803 converts rotational input to the drive shaft5802 via an off-set cam 5804 spinning in a transverse slot 5814 in thecartridge 5800. The drive cam 5803 is supported in a bearing 5808 placedin a countersunk hole 5812 in the frame 5805 and held in place with awasher 5806 and a retainer 5807.

As material is removed from the femoral condyle it is desirable toincrease the height of the shaver accordingly that is to extend theshaver within the tibiofemoral compartment. The cartridge 5800 is freeto move vertically in the frame 5805. One or more shims 5801, eachhaving two arms 5811 designed to pass along side the drive cam 5803, canbe placed between the cartridge 5800 and frame 5805 to extend theshaver.

The description above is provided in order to illustrate variousexamples and embodiments of the invention and is not an exhaustive listof all combinations and variations of the present invention. It shouldbe understood that various changes, adaptations and modifications may bemade therein without departing from the spirit of the invention and thescope of the appended claims. The scope of the invention is provided inthe claims which follow.

1. A method of sculpting the articular surface of a first bone thatnormally articulates in a predetermined manner with a second bone, themethod comprising: fixing a bone-sculpting tool to the second bone;sculpting the articular surface of the first bone; and applying adistracting force between the bone-sculpting tool and the second bone soas to force the bone-sculpting tool into the first bone, in which theforce applying is operated at least in part under load control.
 2. Themethod of claim 1, in which the applying the distracting force includesapplying a fluid under pressure, and in which the load control includescontrolling the fluid pressure.
 3. The method of claim 1, in which thecontrolling the fluid pressure includes controlling a gaseous fluidpressure.
 4. The method of claim 1, in which the controlling the fluidpressure includes controlling a liquid fluid pressure.
 5. The method ofclaim 1, in which the load control includes measuring the load betweenthe two bones and controlling the distracting force at least in part asa function of the measured load.
 6. The method of claim 1, in which theforce applying is controlled under load control, followed bydisplacement control after a displacement limit is reached.
 7. Themethod of claim 6, in which the displacement control includesmechanically limiting the range of displacement.
 8. The method of claim1, in which the load control is at least in part performed by anautomatic controller which automatically controls the distraction forceat least in part as a function of the load.
 9. The method of claim 1, inwhich the load control is at least in part performed under manualcontrol, in which a human controls the distraction force at least inpart in response to a load read-out value.
 10. An apparatus for cuttinginto mammalian bone, the apparatus comprising: a frame having a spacewithin and an outside region without; a plurality of cutting cylindersrotatably disposed within the frame; and a drive member externallyaccessible from outside of the frame, the drive member operably coupledto rotate the cutting cylinders.
 11. The apparatus of claim 10, in whichthe housing has a posterior region for inserting into a mammalian body,an anterior region opposite the posterior region, a right side and aleft side both extending between the posterior and anterior regions, inwhich the drive member is a shaft which protrudes outside of the housingthrough the right and/or left sides.
 12. The apparatus of claim 10, inwhich the drive member is operably coupled to the cutting cylindersthrough gears.
 13. The apparatus of claim 10, in which the drive memberis operably coupled to the cutting cylinders through a flexible driveloop.
 14. The apparatus of claim 10, further comprising a fluid inletport and outlet port in fluid communication with the housing interiorfor providing irrigation.
 15. The apparatus of claim 10, furthercomprising a plurality of nested telescoping platforms, the platformshaving an interior, an extended configuration and a collapsedconfiguration, in which the platforms can be urged from the collapsedconfiguration to the extended configuration through direct or indirectapplication of fluid pressure to the platforms interior.
 16. Theapparatus of claim 10, referring to the barrel cutter of claim 1 as thefirst barrel cutter, further comprising a second barrel cutter coupledto the first barrel cutter so as to transfer applied torque between thefirst and second barrel cutters.
 17. The apparatus of claim 10, in whichthe frame has a length of between about 10 mm and 90 mm, and a width ofbetween about 10 mm and 50 mm.
 18. The apparatus of claim 10, in whichthe frame has a length of between about 10 mm and 90 mm, and a width ofbetween about 40 mm and 100 mm.
 19. The apparatus of claim 10, in whichthe frame has a length of less than about 10 cm and a width of less than10 cm.
 20. A method of removing bone comprising applying the apparatusof claim 10 to bone.
 21. An apparatus for cutting into mammalian bone,the apparatus comprising: a frame having a posterior region forinserting into a mammalian body and an anterior region opposite theposterior region; at least one upper cutting element having a cuttingsurface; and an extendable body operably coupled to the bottom portion,the extendable body having a first configuration, and a secondconfiguration, in which the apparatus has a greater height in the secondconfiguration than in the first configuration, in which the extendablebody is mechanically restricted with respect to side-to-side movement.22. The apparatus of claim 21, in which the extendable body is directlycoupled to the housing.
 23. The apparatus of claim 21, in which theextendable body is at least partially received within the housing. 24.The apparatus of claim 24, in which the extendable body includes abellows.
 25. The apparatus of claim 24, in which the bellows includesinward and outward folds.
 26. The apparatus of claim 21, in which theextendable body includes at least one leg received into the housing. 27.The apparatus of claim 21, in which the extendable body includes anexpandable envelope.
 28. The apparatus of claim 21, in which theextendable body includes at least two nested structures, one at leastpartially nested within the other.
 29. The apparatus of claim 21,further comprising a drive member operably coupled to the cutter elementso as to move the cutting element, in which the drive member isaccessible from outside of the frame.
 30. The of apparatus of claim 21,in which the cutting element includes a cutting element selected fromthe group consisting of cutting cylinders, cutting belts, andreciprocating cutting planar surfaces.
 31. The apparatus of claim 21, inwhich the frame has a length of between about 10 mm and 90 mm, and awidth of between about 10 mm and 50 mm.
 32. The apparatus of claim 21,in which the frame has a length of between about 10 mm and 90 mm, and awidth of between about 40 mm and 100 mm.
 33. The apparatus of claim 21,in which the frame has a length of less than about 10 cm and a width ofless than 10 cm.
 34. A method of removing bone comprising applying theapparatus of claim 21 to bone.
 35. The apparatus of claim 21, furthercomprising an irrigation inlet port, an irrigation outlet port, and anirrigation flow path therebetween adapted to flush bone and tissuepieces from the apparatus.
 36. An apparatus for simultaneously cuttinginto two distinct regions of mammalian bone, the apparatus comprising: afirst frame having a posterior region for inserting into a mammalianbody and an anterior region opposite the posterior region; a secondframe having a posterior region for inserting into a mammalian body andan anterior region opposite the posterior region; the first frame havinga first moveable cutting body including a first upper cutting surfacecapable of cutting into tissue and bone; the second frame having asecond moveable cutting body including a second upper cutting surfacecapable of cutting into tissue and bone; a first drive member operablycoupled to the first cutting body; a second drive member operablycoupled to the second cutting body; and at least one connecting memberfor maintaining the first and second frames in spaced apart relation toeach other.
 37. The apparatus of claim 36, in which the first and secondmoveable cutting bodies are each a rotating cylinder having cuttingsurfaces.
 38. The apparatus of claim 36, in which the first and secondmoveable cutting bodies are reciprocating cutting surfaces each bearingcutting elements.
 39. The apparatus of claim 36, in which the first andsecond moveable cutting bodies are each closed loop belts bearingcutting elements, wherein the belts are driven by the drive members tomove in a longitudinal direction.
 40. An apparatus for cutting intomammalian bone, the apparatus comprising: a frame having a posteriorregion for inserting into a mammalian body and an anterior regionopposite the posterior region; a posterior roller rotatably coupled tothe frame posterior region; a anterior roller rotatably coupled to theframe anterior region; a cutting belt looped around both the posteriorand anterior rollers; and a drive member operably coupled to theanterior roller to rotatably drive the anterior roller and cutting belt.41. The apparatus of claim 40, in which the cutting belt includes aplurality of apertures therethrough.
 42. The apparatus of claim 41, inwhich the cutting belt apertures have a raised trailing edge.
 43. Theapparatus of claim 40, further comprising a posterior tissue protectorcoupled to the frame to protect tissue from the cutting belt posteriorregion.
 44. The apparatus of claim 40, further comprising an anteriorframe member coupled to the frame anterior portion.
 45. The apparatus ofclaim 40, in which the drive member is externally accessible fromoutside the frame, and in which the drive member is disposed along ananterior-posterior axis.
 46. The apparatus of claim 40, in which thedrive member is externally accessible from outside the frame, and inwhich the drive member is disposed perpendicular to ananterior-posterior axis.
 47. The apparatus of claim 40, furthercomprising a housing base operably coupled to the frame for protectingtissue from a bottom portion of the cutting belt.
 48. The apparatus ofclaim 40, further comprising a tensioning arm operably coupled to theanterior and posterior roller for adjusting belt tension.
 49. Theapparatus of claim 40, referring to the apparatus of claim 1 as thefirst belt cutter, further comprising a second belt cutter coupled tothe first belt cutter so as to transfer applied torque between the firstand second belt cutters.
 50. The apparatus of claim 40, in which theframe has a length of between about 10 mm and 90 mm, and a width ofbetween about 10 mm and 50 mm.
 51. The apparatus of claim 40, in whichthe frame has a length of between about 10 mm and 90 mm, and a width ofbetween about 40 mm and 100 mm.
 52. The apparatus of claim 40, in whichthe frame has a length of less than about 10 cm and a width of less than10 cm.
 53. A method of removing bone comprising applying the apparatusof claim 40 to bone.
 54. The apparatus of claim 40, further comprisingan irrigation inlet port, an irrigation outlet port, and an irrigationflow path therebetween adapted to flush bone and tissue pieces from theapparatus.
 55. The apparatus of claim 40, in which the cutting belt hasa longitudinal axis, a substantially planar surface, and a plurality ofouter cutting ridges disposed on the belt outer surface.
 56. Theapparatus of claim 55, further comprising a plurality of inner ridgesdisposed on the belt inner surface.
 57. The apparatus of claim 55, inwhich the ridges are oriented substantially perpendicular to the beltlongitudinal axis.
 58. The apparatus of claim 55, in which the ridgesare oriented at between about a 20 and a 70 degree angle with respect tothe longitudinal axis.
 59. The apparatus of claim 40, in which the belthas a first set of substantially parallel cutting ridges on the beltouter surface, and in which the belt has a second set of substantiallyparallel cutting ridges on the belt outer surface, in which the firstand second set of ridges cross each other to form a diamond shapepattern.
 60. The apparatus of claim 55, in which the belt has a firstset of substantially parallel ridges on the belt outer surface, and inwhich the belt has a second set of substantially parallel ridges on thebelt outer surface, in which the first and second set of ridges aredisposed at least a 20 degree angle with respect to each other. 61 Theapparatus of claim 40, in which the cutting belt includes an abrasivecutting surface.
 62. An apparatus for cutting into mammalian bone, theapparatus comprising: a frame having a posterior region for insertinginto a mammalian body and an anterior region opposite the posteriorregion; a substantially planar upper cutting element having a cuttingsurface; and a drive member operably coupled to the cutter element so asto drive the cutting element to move substantially within a plane, inwhich the drive member is accessible from outside of the frame.
 63. Theapparatus of claim 62, in which the drive member operable coupling isthrough an offset or eccentric cam.
 64. The apparatus of claim 62, inwhich the drive member is disposed along an anterior-posterior axis. 65.The apparatus of claim 62, in which the drive member is disposedorthogonal to an anterior-posterior axis.
 66. The apparatus of claim 62,comprising at least 2 upper cutting elements, each configured to operatein substantially the same plane.
 67. The apparatus of claim 62 in whichthe upper cutting element cuts primarily only when moved in onedirection, but not the opposite direction.
 68. The apparatus of claim 62in which the upper cutting element cuts when moved in one direction andalso in the opposite direction.
 69. The apparatus of claim 62, in whichthe frame has a length of between about 10 mm and 90 mm, and a width ofbetween about 10 mm and 50 mm.
 70. The apparatus of claim 62, in whichthe frame has a length of between about 10 mm and 90 mm, and a width ofbetween about 40 mm and 100 mm.
 71. The apparatus of claim 62, in whichthe frame has a length of less than about 10 cm and a width of less than10 cm.
 72. A method of removing bone comprising applying the apparatusof claim 62 to bone.
 73. The apparatus of claim 62, further comprisingan irrigation inlet port, an irrigation outlet port, and an irrigationflow path therebetween adapted to flush bone and tissue pieces from theapparatus.
 74. An apparatus for cutting into mammalian bone, theapparatus comprising: a frame having a posterior region for insertinginto a mammalian body and an anterior region opposite the posteriorregion; a removable cartridge having an upper surface bearing aplurality of cutting elements, the cartridge slidably coupled to theframe to allow for movement of the cutting elements with respect to theframe; and a drive member operably coupled to the cartridge so as toreciprocatingly drive the cartridge, in which the drive member isaccessible from outside of the frame.
 75. The apparatus of claim 74, inwhich the drive member is rotatably coupled to an off-center cam and theoff-center cam reciprocatingly drives the removable cartridge.
 76. Theapparatus of claim 74, in which the apparatus has a protected,non-cutting posterior end region for protecting tissue.